Ever want to know how to make a cupcake in a jar without having to stick the jar itself in the oven? Here's a great post on how to do it. I recently purchased one of these lovelies from someone online. Through my experience with it, I recommend going a little lighter on the frosting, or doing multiple layers. Perhaps make the frosting "airy" and don't pack it, there is nothing worse then a mouth full of thick frosting with no cake in it!
Once you have the idea down, play around with it and try a recipe that is a little more healthy! The one above uses Paula Deans.
Here's one from Eating Well